(i) Field of the Invention
This invention relates to metal refining in a molten metal bath into which oxygen is injected.
(ii) Description of the Prior Art
U.S. Pat. No. 3,706,549, the teaching of which is hereby incorporated herein by reference, describes the injection of oxygen into a bath of molten metal from below the bath surface in the refining of pig iron to steel, such that accelerated erosion of the refractory used to line the container of the bath, is prevented.
The oxygen injector which extends through the refractory wall lining of the container, comprises two concentric tubes. The inner tube is used for injection of oxygen gas and the annular space between the inner tube and the outer tube is for applying a protective fluid. The fluid, which is usually a hydrocarbon, is employed to shield the oxygen from the reactive molten metal at the interface of the refractory wall and the molten metal and ensures that the vigorous reaction with the molten metal takes place away from the refractory wall.
The resultant delay in the exothermic reaction between the oxygen and the molten metal is sufficient to maintain the integrity of the refractory wall.
The prior art teaches that the effectiveness of the hydrocarbon protective fluid shield is due to its endothermic decomposition under the high temperature conditions existing in the molten metal bath.
Although use of the method of the U.S. Patent results in an overall improvement, particularly in the life of the refractory, the injector is still subject to erosion and it is desirable to further improve the life of the refractory lining.
It is an object of this invention to improve the life of an injector and of the refractory lining employed in a method of the kind described in U.S. Pat. No. 3,706,549.